> Why do you think modern CPUs still expose mostly C-abstract-machine-like interface

I don’t think that, because they don’t. Your premise is hogwash.

Modern RISC derived CPUs for the most part expose a load store architecture driven by historical evolution of that micro arch style and if they are SMP a memory model that only recently has C and C++ adapted to with standards. Intels ISA most assuredly was not influenced by C. SIMD isn’t reminiscent of anything standard C either.

Also you might want to look into VLIW and the history of Itanium for an answer to your other question.